From 7ff394e1ecab504a4cb0fda4bd0f25d88ee4f6fe Mon Sep 17 00:00:00 2001
From: Timo Rothenpieler <timo@rothenpieler.org>
Date: Mon, 14 Jul 2025 21:54:35 +0200
Subject: [PATCH] avformat/flvdec: don't skip backwards or at EOF

---
 libavformat/flvdec.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/libavformat/flvdec.c b/libavformat/flvdec.c
index b90ed34b1c..de5e688822 100644
--- a/libavformat/flvdec.c
+++ b/libavformat/flvdec.c
@@ -1860,8 +1860,16 @@ retry_duration:
 next_track:
         if (track_size) {
             av_log(s, AV_LOG_WARNING, "Track size mismatch: %d!\n", track_size);
-            avio_skip(s->pb, track_size);
-            size -= track_size;
+            if (!avio_feof(s->pb)) {
+                if (track_size > 0) {
+                    avio_skip(s->pb, track_size);
+                    size -= track_size;
+                } else {
+                    /* We have somehow read more than the track had to offer, leave and re-sync */
+                    ret = FFERROR_REDO;
+                    goto leave;
+                }
+            }
         }
 
         if (!size)
-- 
2.49.0